Radio tuning device



July 4, 1933. W D I 1,917,077

RADIO TUNING DEVICE Filed April 30, 1930 4 Sheets-Sheet l 02%!275/9ea/ye 71 042 W W G. WALD RADIO TUNING DEVICE July 4, 1933.

Filed April 30, 1930 4 Sheets-Sheet 2 yea/ye 71 4/51 July 4, 1933. G.WALD 1,917,077

RADIO TUNING DEVICE Filed April 30, 1930 4 Sheets-Sheet 3 Gear e Wa/a:

July 4, 1933. s. WALD RADIO TUNING DEVICE Filed April 30, 1930 4Sheets-Sheet 4 ur- M).

Patented July 4, 1933 GEORGE WALD, or 'BELLEVILLE, ILLINOIS RADIO TUNHVGDEVICE Application filed April 30,

This invention relates to improvements in radio tuning devices, andconsists in the novel construction hereinafter disclosed.

An object of the invention is to provide, in a tuning system for radioreceiving circuits, a tuning device comprising a helical condenserincluding a plurality of units whereby separate stages of radiofrequency, or separate stages of radio frequency and an oscillatorcircuit, may be simultaneously tuned for the reception of wave lengthsof wide variation.

A furtherpbject of the invention is to provide a novel construction of ahelical condenser unit that is compact in construction and which may beeconomically manufactured for quantity production.

Another object of this invention is to provide a novel radio receivingvset capable of accurate tuning and with which reception is possiblethroughout a wave band of 10 to 600 meters.

Additional objects of theinvention will be readily apparent to thoseskilled in the art from the following detailed description thereof,taken in connection with the accompanying drawings, in which ig. 1 is aside elevation of the condense unit shown in association with thecontrolling means therefor.

Fig. 2 is a diagrammatic View of one form of radio receiving circuitwith which the condenser, constituting the tuning unit, is associated.

Fig. 3 is a diagrammatic view of the transformer in an oscillator orradio frequency circuit.

Fig. 4 is a detail view of an alternate form of actuator and dial drumfor the condenser unit.

Fig. 5 is a detail view illustrating a feature of construction of thestator of the condenser. Fig. 6 is a further detail view of the sameconstruction.

Fig. 7 is an isometric View showing the manner in which the plates ofthe stator of the condenser are assembled.

Figs. 8 to 13, inclusive, show the progressive forms of plates formingthe helix of the condenser stator.

The condenser which comprises the tuning unit for the receiving circuit,as shown in the drawings, includes a frame having a base 1 adapted tosupport'the unit in the case of a radio receiving set. Integrally formed1930. Serial no. 448,462.

with the base 1 are standards 2, 3 and 4. The standards 2 and 3constitute the end members of the condenser frame, and the standard 4constitutes a journal support for the rotor of the condenser. Thecondenser cage supporting the stator plates comprises circular endplates 5 and 6 of electrically non-conductive material and bars orstrips 7 extending longitudinally between the members 5 and 6 andsecured, respectively, to the peripheries thereof. The strips 7 arespaced equally circircumferentially at 60 apart. The condenser cage issecured in the condenser frame by a pair of screws 8 that extend throughthe standard 3 into the end member 5 and a pair of screws 9 that extendthrough the standard said shaft being supported in the plate 6 in whichit is rotatively mechanically secured and the other end extending forsome distance into the condenser cage. This shaft 13 is non-rotated, however,exce t for the slight adjustment hereinafter escribed. This shafthas a spiral slot 14 cut in its face.

A revoluble shaft 15 extends into the opposite end of the'condenser cageand has an v2 and through a spacing block 10 and into the extension thatis journaled for rotation in the standards 3- and 4. The inner end ofthe shaft 15 carries a sleeve 16 which is cou pled with the shaft 15 bya pin-and-slot con-' nection 17. The sleeve 16 constitutes the hub ofthe rotor helices of the condenser and for the dial drum.

The sleeve 16 has a pin 18 on its inner face and near its open end, saidpin 18 being adapted toride in the spiral slot 14. Thus, as the shaft 15is rotated in one direc tion, the sleeve 16 by reason of the pin-andslotconnection 17 will rotate with the shaft and will travel inwardly byreason of the pin 18 riding in the slot 14. When the shaft 15 is rotatedin the opposite direction the sleeve 16 will move outwardly from theshaft 13. The rotor elements of the condenser are carried by the sleeve16. and by the operation of the shaft 15 will be moved into and out ofcondensive relationship with the stator elements to a greater or lesserdegree, as will be more fully hereinafter explained.

Any suitable means may be provided for rotating the shaft 15. In theembodiment shown in Fig. 1 of the drawings the actuator for the shaft 15comprises a pulley 19 supported on a shaft 20 which shaft may berevolved by a knob (not shown) accessible from the outside of the .radioreceiving set case The pulley 19 is operatively connected with a pulley21, pinned 'to the shaft 15, by a flexible connection 22. The faces ofthe pulleys 19 and 21 may be arranged at any suitable angle so as toposition the operating knob at a convenient place in the panel of theradio receiving set case. The shaft 15 is held in proper longitudinaladjustment by collars 23 and 24 pinned to said shaft 15 and abuttingrespectively against the faces of the shaft journals in the standards 3and 4.

In Fig. 4 of the drawings a modification of the arrangement foroperating the condenser shaft is shown, and in this figure is also shownan alternate arrangement of an indicating drum- In this embodiment apulley, corresponding to the pulley 19 and therefore similarilynumbered, is operatively connected with a pulley on the shaft 15corresponding to the pulley 21 and therefore similarly numbered and witha separate pulley 25 which operates a shaft 26 on which the dial drum iscarried. The connection for operating the pulleys 21 and 25 comprises aflexible connection corresponding to the connection 22 and thereforesimilarly numbered. The differences between this construction and theconstruction shown in Fig. 1 is that the ratio between the pulleys 21and 25 is such that the degree of rotation of the pulley 25 is half thatof the pulley 21. Therefore, the dial travels half the rate of thetravel of the condenser rotor; whereas in Fig. 1 the dial is carriedbythe sleeve 16, and therefore makes the same number of turns as the rotorand advances with it.

The shaft upon which the pulley 19 of Fig. 4 is mounted corresponds tothe shaft 20 of Fig. 1 and therefore is similarly numbered. In Fig. 4this shaft is shown as operated by a knob 27 on the outside of the panelof the radio receiving set case.

In Fig. 1 the dial is in the form of a cylinder on the periphery ofwhich there is a spiral scale, said dial being mounted upon the end ofthe sleeve 16 and turning there with. In Fig. 4 a similar scale (notshown) is mounted on a drum that is carried by the shaft 26. The dial inboth instances constitutes means for guiding the adjustment of the rotorof the condenser.

The stator'portion of the condenser that is supported in the condensercage 15 constructed in a novel manner and includes gen-- erally threeconsecutive series of plates, the

forms of which are shown specifically in Figs. 8 to 13 of the drawings,so "arranged as to form three separate helices. The plates are desi nedto be formed from sections stamped by standard dies which when assembledform a helix of increasing area. -As specifically shown, each helixconsists of six plates, the form of each being shown respectively inFigs. 8 to 13, inclusive. They may be punched from flat stock and thendeformed to constitute a part of a continuous helix. The split ends aredeflected to give a pitch of approximately three-eighths of an inch tothe helix thread. Each plate is provided with lugs 29, 30 and 31 bymeans of which they are secured in slots formed in theinner face of themember 7.

The method of assembling the plates to form the threehlices is asfollows:

A series ofthree plates, as shown in Fig. 8, are placed side by side inthe condenser cage. The three plates of Fig. 8 are then placed in thecondenser cage so that the lugs 29, 30, and 31, seat in slots formed inthe inner face of the members 7, the lugs 29 of each of the three platesbeing displaced 120 from each other.- The remaining plates shown inFigs. 9 to 13, inclusive, are similarly assembled, the lugs 29, 30- and31, being placed in the same respective slots as the corresponding lugson other plates of the same series. The plates of each helix are matchedat their ends thereby-forming three continuous helices arranged side byside and interthreaded, each helix increasing in area from its inner endtoward the outer end thereof. All of the lugs 29 of each series are incontact with the respective inset con-.

ductor bars 12 in the members 7, and the corresponding lugs 30 and 31contact with the diametrically opposite bars 12.

In assembling the plates in the condenser I cage a spacing templatemaybe used to prop- I erly position the lugs in the respective slots inwhich they are mounted and, after the plates are positioned, they may besoldered in place, or spacing washers may be used between the plates andthey may be clamped in place by' a suitable construction, if de-' sired.It will thus be seen that the three stator units are secured in thecondenser cage so that the beginning of each stator unit, as well astheir termination, is 120 apart. Or the beginning of all the stator androtor units may be on the same line, but the stator plates so stampedout as to have lugs 29, 30 and 81 of each unit displaced 120 on theircircumferences.

Three leads 32, 33 and 34 are taken ofl the respective bars 12 forconnecting the separate stator units of the condenser into theradioreceiving circuit, as will be more fully ex plained hereinafter.

The rotor of the condenser is made up of three helices similarlyassembled from series of similar plates, except that the plates of therotor are uniform in area. The three the rotor plates in said grooves.

It should be noted, therefore, that in the construction of the statorand rotor units of the condenser there is provided three series ofhelices for the stator. which are adapted to be brought into condensiveinter-relation with the three helices of the rotor. The condensivesurface relationship between the rotor plates and the stator platesgradually increases as the rotor is moved into the stator by therotation of the shaft in one direction, and decreased as the shaft isrotated in the opposite direction.

The distance between the rotor and stator plates is approximatelyone-sixteenth of an inch less the thickness of two plates. This distancemay be slightly regulated by a con struction for adjusting the rotativeposition of the shaft 13. The shaft 13 extends through the end plate 6and is provided with a knurled knob by which it may be given a slightrotation to change the relationship of the slot 14 to the thread ofthestator helices. A set screw 36 extends through a slot 37in the knob35 and into the plate 6 and provides means for setting the adjustmenteffected by the knob- 35, which adjustment is limited by the length ofthe slot 37.

The platcsshown in Figs. 12 and 13 may preferably be made of a. greaterthickness than the remaining plates, and, therefore,

the dielectric space between the rotor and stator plates is reduced.This results in an effective capacity for these plates double that ofthe area. The result of this is that tuning can be effected by the lastthree turns of the condenser to a wave band of from 200 to 600 meters,while the first three turns are utilized to tune in a wave band of 10 to150 meters.

In place of arranging the plates'of the condenser stator in interfittingrelationship,

they may be arranged in consecutive longitudinal positions and theplates of the rotor may also be arranged in corresponding 1ongitudinalalignmentto cooperate with the separated stator units, in which eventthe pitch of the helices of both the rotor and the stator may bedecreased. The modified form of actuator illustrated in Fig. 4 may beutilized with this construction so that the dial may have the scale withsuitable intervals to indicate the position of the condenser elements.

In Fig. 2 of the drawings there is illustrated a radio receiving circuitinto which the condenser of the construction hereinbefore described isconnected. It willbe unnecessary to describe the various circuits as theundescribed portion of the diagram will be readily recognized as thestandard con- 7 struction of a heterodyne circuit. The manner in whichthe condensers are connected into the receiving circuit, together withthe control of the secondary of an oscillator clr- -cuit and of one ofthe radio frequency circuits before the detector, provides for tuningthe receiving set to a wide variation of radio frequency. This isaccomplished by controlling the induction of the secondary of theoscillator and the radio frequency circuits and by controlling thecapacity of the condenser in co-ordination with the induction. Arepresents the oscillator circuit and B and C represent the radiofrequency circuits with which we are primarily concerned.

In Fig. 3 of the drawings is shown a diagram of the particular form oftransformer employed both in the oscillator and radio frequency circuitsA and B.

By reference to the circuit B it will be noted that the circuit consistsof an untuned vacuum tube 38, the plate of which connects through aprimary 39 to 13+ 160 v. The primary has, for example, twenty totwenty-five turns and is wound on a spool or holder 40 (Fig. 3), whichspool or ho der also carries a part of the secondary winding. Theprimary and the portion of the secondary that is wound on the spool 40has a one to one ratio and has an induction of approximately 103 m.henries. Adjacent to the spool 40 and in the same magnetic'path is asecond spool 41 upon which is wound the remainder of the secondary, forexample, to turns, and has an induction of approximately 205 1n.henries;

.The windings of the secondary on the I spool 40 1s lndlcated by 42(Fig. 2) and that portion of the secondary wound on the spool 41 isindicated by 43 (Fig. 2). It will be understood that the magnetic pathbetween the two portions of the secondary is continuous. Therefore, thetotal induction when both portions of the secondary are connected is thesum of their separate induction or approxlmately 308 m. henries. Theportion of the secondary 43 is cut in and out by the switch 44. Thetransformer therefore may be controlled to provide an induction eitherof 103 in. henries or 308 In. 'henries, for example.

By reference to Fig. 2 it will be noted that the switch 44 is soconnected with the second radio frequency circuit C that when the sw tchis down the. second stage of radio frequency is cut out.

When the leads 32, 33 and 34 from the respective helices ofthe-condensrr are connected to the circuits B, C and A, respectively, asshown in Fig. 1, the capacity and inductance of the circuitsare balancedto produce resonance at predetermined frequencies in any rotation of thecondenser, i. e. the inductance in each of the circuits being the sameand an equal amount of capacity being added at all times to'produceresonance for the selected frequency. By operating the switch 44 theinduction in the circuits A and B are reduced because of cutting out thesupplemental turns of the secondaries of their transformers and thecircuit C is cut out.

The following table gives the capacity in m. farads required for thenecessary resonance of a circuit when employed with the transformerspecifically illustrated and described adapted to produce an inductanceL of either 308 or 103 m. henries, in order to tune to the various wavelengths or frequencles as indicated in the table Approximate .WaveFrequencapacity regg ga g gg' length in cies in quired when g g' 103meters k.c. L 308 m. m hemies henries 600 500 000375 m.f. 500 600 000268mi. 400 750 000102 m.f. 300 1, 000, 000095 mi. 200 1, 500 000045 IlLf.150 2, 000 000024 mi. 00007 mi. 000027 m.f. 000017 mi. 000011 IILf.000008 IILf. 000005 mi. 000003 1111. 0000014 IILf. 00000048 mi. 00000027m.f.

In the following table is shown the areas of the plates illustratedrespectively in Figs.

' 8 to 13 of the drawings, assuming an exterior diameter of 4.5 inchesand approximate interior diameters as shown in the second column. In thelast column is shown the capacity of the condenser when a rotor fheliXhas been advanced in steps respectively so that it adjoins the severalplates. The capacities for plates Nos. 12 and 13 are based uponcorrected computations due to a narrower air gap ad acent those plates,as .described above:

Approx- Approximate imate average area 33: interior (one g diamside)etersq. inches inches By a comparison ofthe above tables, it will beseen that the construction of the condenser is such as to provide agraduated capacity suficient withthe two inductance values to permit thetuning of a circuit for'the full wave band for 10 to 600 meters.

From the foregoing description it will be apparentthat the inventionaccomplishes its object.

While a particular radio receiving circuit is shown, the application ofthe invention is not limited to that particular circuit, but as may beapparent, the invention is applicable to a wide range of receivingcircuits employing balanced circuits. It is to be understood thatotherwise the invention is not limited to the details as shown anddescribed, but that partsof the invention may be used to advantagewithout the whole, and that various changes may be made in the detailsof construction within the scope of the appended claims Withoutdeparting from the scope of this invention.

1 claim: 0 v

1. A condenser having a pair of helical plates, and means forprogressively advancing one plate into position with the other, one ofsaid plates comprising a plurality of circular sections distorted toform an integral part of a helix, each of said sections having an endcoincident with an end of an adjacent section, and one of said sectionsbeing thicker than others to reduce the air gap between it and thecooperating plate.

2. A condenser comprising a plurality of helical stator plates inintertwined relationship, a plurality of helical rotor plates inintertwined relationship carried by a common supporting element, each ofsaid rotor plates being adapted to cooperate with a stator plate, andmeans for simultaneously rotating and longitudinally moving saidsupporting member whereby each of said rotor plates will besimultaneously moved into cooperation with a stator plate.

3. A condenser'comprising a plurality of helical stator plates inintertwined relationship, a plurality of helical rotor plates inintertwined relationship carried by a common supporting element, each ofsaid rotor plates being adapted to cooperate with. a stator plate, meansfor simultaneously rotating and longitudinally moving said supportingmember whereby each of said rotor plates will be simultaneously movedinto cooperation with a stator plate, and an indicating drum mounted onsaid supporting member.

4. A condenser comprising a plurality of like helical stator plates inintertwined relationship, a plurality of helical rotor platescorresponding in pitch and relationship to said stator plates, a commonmounting for said rotor plates, and means to cause rotation.

and longitudinal movement of said mount-' ing.

GEORGE WALD.

